A simple explanation of how my brain understood, accepted, and decided on the answer follows:

1st, the stimulus states that a person who is willing to make fun of their self in a humorous way is self-confident. 2nd, the stimulus points out that a person who allows others to make fun of them in a humorous manner is also confident, although maybe not as confident.

The stimulus gives us the equation for noticing self-confidence:

Making fun of yourself, or allowing others to make fun of you = self-confidence

The opposite, or negated, form of this equation is:

no self-confidence = not making fun of yourself, nor allowing others to make fun of you.

The negated form of the stimulus is precisely what answer choice (A) states. Since the question wants an answer that has the most support from the stimulus, the negation of the explicitly given equation is the perfect choice.